ABSTRACT
Angiotensinogen (AOG) is the glycoprotein precursor of the angiotensin peptides. It is cleaved by renin to yield the decapeptide angiotensinI (AngI); angiotensin-converting enzyme then removes a dipeptide from the C-terminal end of AngI to form the physiologically active octapeptide angiotensin II (AngII). Circulating AngII increases vascular tone and promotes salt and water retention by a combined action on many target organs, including vascular smooth muscles, kidneys, adrenals, brain, and sympathetic nervous system. The stimulatory effects of estrogens on circulating levels of AOG were first reported by Helmer and Griffith. This has been confirmed in many subsequent reports; in addition, synthetic steroids were found to be more effective than naturally occurring steroids. AOG is produced in tissues other than liver as well. The importance of extrahepatic production of AOG has not been determined, but it is conceivable that the concentration of AOG is higher in tissues producing this protein than in those that receive the protein only from the circulation.
